These blessings and curses are similar to a key part of ancient Near Eastern treaties between a suzerain (a powerful king) and a vassal (a lesser king). In these treaties, the suzerain king promised to protect the vassal king and his land. In return, the vassal swore loyalty to the suzerain.
Blessings and curses followed, with curses usually being longer (compare Leviticus 26:3–13 with 26:14–39; see also Deuteronomy 27:15–28:68). These treaties often called upon gods as witnesses and enforcers. Yet, in God's covenant with Israel, God was one of the treaty parties, with Israel as the other. Since God could not swear by anyone greater, he swore by himself (see Hebrews 6:13; Genesis 22:16).